1. Field of the Invention
The present invention is generally directed to the field of semiconductor fabrication. More particularly, the present invention is in the field of plasma etch tools for semiconductor fabrication.
2. Related Art
Plasma etch tools have a tendency to generate electric arcs during long high bias processes. Arcing is caused by a higher than desired charge building up on the chuck upon which the wafer is mounted during processing. When the charge built up on the chuck reaches a critical voltage potential difference from the etch tool plasma, an electric arc is generated from the plasma through the wafer to the chuck to dissipate this voltage potential difference. Arcing during plasma processing requires the processed wafer to be scrapped. Further processing of wafers that need to be scrapped wastes time and resources. Also, allowing wafer processing to continue during arcing will cause additional wafers to be scrapped, which lowers the useful yield of the fabrication process and undesirably increases manufacturing costs.
Makers of plasma etch tools have focused on reducing the number of arcing incidents, but these solutions have not resulted in elimination of arcing events, and arced wafers continue to be discovered too late, after completion of an entire time-consuming wafer processing run. A real-time data acquisition tool was developed so that semiconductor fabrication personnel could detect wafer arcing by monitoring the conditions that affect arcing. However, real-time data monitoring requires that a person be present and alert to monitor the etch tool during the entire wafer processing, which can last several hours. Thus, the human-monitor approach is costly and subject to human error. Another approach similar to the human-monitor approach utilizes a computer system to oversee the monitoring and control process instead of a person. However, this approach is costly since it must be customized for each application and requires a computer system.
Thus, there is a need in the art for a cost-effective device that can accurately detect arcing in an etch tool during wafer processing.